The present invention refers to a device for the transmission of information through the rails between a railway track and a group of vehicles running in the same direction along this track over the length of which a plurality of zones for the transmission of information succeed one another.
Railway tracks and mainly those having heavy traffic are usually equipped with a block system, especially by track circuits, which in general employs the running rails as the path of transmission.
In modern equipment it has become necessary to have a device for transmission of information between the track and the vehicles. Such a device is capable of coexisting with the block system and, the whole system operating in a fail-safe manner in the railway sense of this term.
A known solution consists in transmitting the information by induction from a cable arranged in the track or along it, but this solution offers a certain number of disadvantages: the costs of the cable and the restraints which result from it in the maintenance of the track.
The employment of the running rails as the transmission path causes these disadvantages to disappear but comes up against two difficulties. The first difficulty arises.
From the fact that the running rails serve as the return circuit for the traction current with electrified lines and very often as the transmission path for the block signals.
Hence the signals of any system of transmission of information through the rails must be superimposed upon these existing currents and signals without disturbing them and must be able to be separated from them.
The difficulty is connected with the division of the track into blocks. This division must not affect the transmission of the information, of which the zones of transmission when this is effected by zones which succeed one another along the track, must be able to be demarcated independently of the sections of the block system.